Advances in Calcareous Nannofossil Biostratigraphy Based on Toarcian–Aalenian Sections in the Lusitanian Basin (Portugal)

Abstract

We performed quantitative analyses of Early–Middle Jurassic calcareous nannofossil assemblages in two sections of the Lusitanian Basin (Portugal) for biostratigraphic purposes. The study was conducted on samples spanning the lower Toarcian to middle Aalenian strata in the Rabacal and Cabo Mondego sections. All samples were quantitatively studied for calcareous nannofossils. The last occurrence (LO) of one species and the first occurrences (FOs) of four species have been recorded in the lower to middle Toarcian section of Rabacal. For the upper Toarcian to middle Aalenian section at Cabo Mondego, the FOs of three species and the LOs of four species were recognized. The continuous calcareous nannofossil record allows both nannofossil biohorizons and zone boundaries to be calibrated with respect to the ammonite zones, and events across the Toarcian and Aalenian stages in the Lusitanian Basin to be precisely identified.